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Prop bolts

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Dick Maddux

Joined: 24 Jun 2008
Posts: 516
Location: Milton, Fl

Posted: Wed Jan 20, 2010 6:30 am Post subject: Prop bolts

The prop flange is part of the engine so I thought I would bring this up here. I am replacing the prop on my aircraft with a Kiev prop (removing my Warp) The prop flange looks like a "swiss cheese" on my older Rotax 912. I have three sizes of holes. The outer holes are bigger and with the Warp I used prop bushings. The Kiev uses 6 of the inner holes (out of the 12) All of the inner holes are threaded and are two different sizes. The ones I use for the Kiev hub take an 8mm bolt as did the Warp (with the bushes) Confused yet ?....me too

  Anyway,I am trying to find good grade 8 ,8mm bolts. The importer says the Chinese are the only ones that have 8mm prop bolts. I don't want to use Chinese prop bolts. I know AN bolts are not metric but does anyone know where I can get the proper bolts ?

                                   Thanks !

                                                     Dick Maddux

                                                     912UL

                                                     Milton,Fl

  [quote][b]

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lucien

Joined: 03 Jun 2007
Posts: 721
Location: santa fe, NM

Posted: Wed Jan 20, 2010 6:47 am Post subject: Re: Prop bolts

[quote="Dick Maddux"]The prop flange is part of the engine so I thought I would bring this up here. I am replacing the prop on my aircraft with a Kiev prop (removing my Warp) The prop flange looks like a "swiss cheese" on my older Rotax 912. I have three sizes of holes. The outer holes are bigger and with the Warp I used prop bushings. The Kiev uses 6 of the inner holes (out of the 12) All of the inner holes are threaded and are two different sizes. The ones I use for the Kiev hub take an 8mm bolt as did the Warp (with the bushes) Confused yet ?....me too

  Anyway,I am trying to find good grade 8 ,8mm bolts. The importer says the Chinese are the only ones that have 8mm prop bolts. I don't want to use Chinese prop bolts. I know AN bolts are not metric but does anyone know where I can get the proper bolts ?

            ï¿½           ï¿½          Thanks !

            ï¿½           ï¿½            ï¿½           ï¿½   Dick Maddux

            ï¿½           ï¿½            ï¿½           ï¿½   912UL

            ï¿½           ï¿½            ï¿½           ï¿½   Milton,Fl

   	  Quote: 	
		  [b] 	




Aircraft grade metric hardware is unavailable in the US. I've looked everywhere for it in the past and got only puppy-dog looks from everyone I've ever asked about it. So forget it 



Your only choice is grade 8.8 8MM bolts available at hardware stores and fastener outfits like Fastenal (highly recommended). Fortunately, those fasteners work just fine, they're plenty strong and the QC on them is generally good enough.



Do NOT use stainless steel bolts _if you use backing locknuts only_ - they're not strong enough with only backing nuts. Don't ask me why I know this. If they thread into something substantial, such as the threads in the prop flange or the lugs in the outer ring if equipped, they'll be fine.



5/16" grade 5 is another option for the unthreaded holes. Do NOT try to thread 5/16" bolts into the threads in the prop flange. Those are 8MM threads. 

AN5 bolts with AN locknuts should work through the appropriate unthreaded holes too, tho the tightening torque specified for most props are for coarse thread. AN bolts/nuts are UNF so you'd have to adjust the tightening torque accordingly to get the same preload. 

LS

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_________________
LS
Titan II SS

rlborger(at)mac.com
Guest

Posted: Wed Jan 20, 2010 7:37 am Post subject: Prop bolts

 	  Quote: 	
		  Dick,



McMaster-Carr has Grade 8.8, DIN 931 (1.25 pitch, partially threaded) and DIN 960 (1.00 pitch, partially threaded) metric bolts.  I have no idea where they are manufactured. I have no idea if they are exactly what you need for prop bolts.  But you can check them out and see what you think.



http://www.mcmaster.com/  Go to Cap Screws.  Scroll down and select Metric under "System of Measurement."  Select Class 8.8 under "Material."  See what they have from there..



Good luck,

Bob Borger

Europa XS Monowheel, Intercooled Rotax 914, Airmaster C/S prop



On Wednesday, January 20, 2010, at 08:20AM, <catz631(at)aol.com> wrote:

 	  Quote: 	
		  	
    The prop flange is part of the engine so I thought I would bring this up here. I am replacing the prop on my aircraft with a Kiev prop (removing my Warp) The prop flange looks like a "swiss cheese" on my older Rotax 912. I have three sizes of holes. The outer holes are bigger and with the Warp I used prop bushings. The Kiev uses 6 of the inner holes (out of the 12) All of the inner holes are threaded and are two different sizes. The ones I use for the Kiev hub take an 8mm bolt as did the Warp (with the bushes) Confused yet ?....me too

   Anyway,I am trying to find good grade 8 ,8mm bolts. The importer says the Chinese are the only ones that have 8mm prop bolts. I don't want to use Chinese prop bolts. I know AN bolts are not metric but does anyone know where I can get the proper bolts ?
	


                                    Thanks !

                                                      Dick Maddux

                                                      912UL

                                                      Milton,Fl

    	  Quote:

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Roger Lee

Joined: 10 Jan 2006
Posts: 1464
Location: Tucson, Az.

Posted: Wed Jan 20, 2010 5:57 pm Post subject: Re: Prop bolts

Hi Dick,



Ace Hardware has these bolts in metric.

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_________________
Roger Lee
Tucson, Az.
Rotax Instructor & Rotax IRC
Light Sport Repairman
Home 520-574-1080 TRY HOME FIRST
Cell 520-349-7056

Dick Maddux

Joined: 24 Jun 2008
Posts: 516
Location: Milton, Fl

Posted: Thu Jan 21, 2010 6:26 am Post subject: Prop bolts

Thanks for the input on the prop bolts guys. What does the 8.8 mean. Does it mean grade 8, and 8mm or has it do do with the thread.

                                           Dick Maddux

                                           Milton Fl

  [quote][b]

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rlborger(at)mac.com
Guest

Posted: Thu Jan 21, 2010 7:02 am Post subject: Prop bolts

 	  Quote: 	
		  Dick,



Check:  http://www.mcmaster.com/param/html/AboutCapScrewMaterial/



McMaster has lots of great information associated with their products on their web site.



Bob Borger

Europa XS Monowheel, Intercooled Rotax 914, Airmaster C/S prop



On Thursday, January 21, 2010, at 08:21AM, <catz631(at)aol.com> wrote:

 	  Quote: 	
		  	
    Thanks for the input on the prop bolts guys. What does the 8.8 mean. Does it mean grade 8, and 8mm or has it do do with the thread.

                                            Dick Maddux
	


                                            Milton Fl

    	  Quote:

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jpkp(at)comcast.net
Guest

Posted: Thu Jan 21, 2010 7:15 am Post subject: Prop bolts

Hi Dick---The numbers on the head of metric capscrews indicate  the strength--In this case, 8.8 tells us that this metric capscrew is equal in  strength to an american made grade 5 capscrew (indicated by 3 equally spaced  radial marks on the head [100,000 to 120,000 lbs. tensile strength]).  10.9  on a metric hex head capscrew equals grade 8 american specs (150,000 to 160,000  lbs/sq. in.).  John Pletting--Vancouver WA.

 [quote]   ---

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lucien

Joined: 03 Jun 2007
Posts: 721
Location: santa fe, NM

Posted: Thu Jan 21, 2010 7:20 am Post subject: Re: Prop bolts

Here's another good basic chart on bolt grades:



http://www.boltdepot.com/fastener-information/Materials-and-Grades/Bolt-Grade-Chart.aspx



The grading system for metric and English sized bolts is slightly different with different units of measurement, etc. But there's a rough equivalence between some of the grades like 8.8 metric vs 5 English.



The grades that manufacturers seem to choose for prop bolts for 912 class props are 8.8 for metric and grade 5 for English. Some manufacturers like Powerfin use stainless steel hardware (with, of course, specific installation requirements like they have to thread into mounting lugs in the flange and have fairly precise torque requirements, etc).



These grades have the ductility required for that application. Harder bolts tend to be too brittle and have more risk of failure.



But by now you should see bolts ain't all that simple  You'd think it wouldn't be so complicated to just bolt a prop onto your airplane, but it is....



LS

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_________________
LS
Titan II SS

Dick Maddux

Joined: 24 Jun 2008
Posts: 516
Location: Milton, Fl

Posted: Fri Jan 22, 2010 4:51 am Post subject: Prop bolts

Thanks for all the input guys ! and as Lucien says " bolts aint so simple"

                                                                    Dick Maddux

                                                                    Milton,Fl

  [quote][b]

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